(a) Field of the Invention
The present invention relates to a base station, a relay station, and a mobile station. More particularly, the present invention relates to a method and apparatus for sending and receiving Multicast Broadcast Service (MBS) data.
(b) Description of the Related Art
A mobile communication system can support a multi-carrier.
In this case, a carrier for non-MBS that chiefly serves unicast and a carrier for MBS may be separately allocated to a mobile station.
However, a mobile station including one transceiver receives only non-MBS data or only MBS data in a specific time interval because it has to receive non-MBS data and MBS data through carrier switching.
Accordingly, an MBS transmitting apparatus needs to perform scheduling in order to transmit non-MBS data and MBS data. However, since the MBS data is transmitted to a plurality of mobile stations, the structure of the MBS transmitting apparatus for scheduling the plurality of mobile stations may become complicated.
Meanwhile, an MBS transmitting apparatus can support a mixed carrier that may include a non-MBS region for transmitting non-MBS data and an MBS region for transmitting MBS data. However, although the MBS transmitting apparatus uses the mixed carrier, the bandwidth may be insufficient to allocate the non-MBS region of the mixed carrier to all mobile stations that receive the MBS data transmitted via the mixed carrier. Consequently, the MBS transmitting apparatus is required to transmit the non-MBS data to some of the mobile stations through a carrier not the mixed carrier. Accordingly, the structure of the MBS transmitting apparatus may become complicated.
A signal transmitted through one carrier supporting MBS may be divided into a plurality of subbands on the frequency axis. All the plurality of subbands may be allocated to an MBS region. Furthermore, the plurality of subbands may be allocated to an MBS region and a non-MBS region or to an MBS region and an unused region. Each region includes at least one subband.
Meanwhile, the MBS region may be divided into a plurality of MBS zones. Each MBS zone includes at least one subband.
Accordingly, an MBS transmitting apparatus is required to send information to an MBS receiving apparatus so that the MBS receiving apparatus can recognize MBS zones and identify each MBS zone based on the information.
Therefore, a method in which an MBS transmitting apparatus provides allocation information of zones and a zone flag indicating whether the last zone is allocated to a non-MBS region to an MBS receiving apparatus may be used.
According to this method, in a network including a zone #1, a zone #2, and a zone #3, the zone #1 and the zone #2 are allocated to MBS, and the zone #3 is allocated to unicast or MBS.
Accordingly, a mobile station served by an MBS transmitting apparatus belonging to the zone #1 and the zone #2 can recognize that the zone #1 and the zone #2 have been allocated to the MBS region based on zone allocation information and can recognize that the zone #3 has been allocated to the non-MBS region based on a zone flag.
However, the mobile station served by the MBS transmitting apparatus belonging to only the zone #1 cannot recognize whether the zone #2 has been allocated to the non-MBS region. Accordingly, the MBS transmitting apparatus belonging to only the zone #1 cannot allocate the zone #2 to the non-MBS region. Furthermore, the mobile station served by the MBS transmitting apparatus belonging to only the zone #2 cannot recognize whether the zone #1 has been allocated to the non-MBS region. Accordingly, the MBS transmitting apparatus belonging to only the zone #2 cannot allocate the zone #1 to the non-MBS region. Accordingly, waste of the bandwidth may be caused.